The present invention relates to a fluorine-containing adhesive which can adhere strongly to a substrate of various inorganic materials or organic materials, particularly to the fluorine-containing adhesive suitable for adhering by thermo-melting. The present invention further relates to a molded article and laminated article which are made by using the fluorine-containing adhesive.
Fluorine-containing polymers have been used for various applications since they are excellent in heat resistance, chemical resistance, weather resistance, surface characteristics (friction resistance, etc.) and electric insulating property.
On the contrary, fluorine-containing polymers are generally insufficient in mechanical strength and dimensional stability, and high in price.
In order to minimize those disadvantages and make the best use of the merits of the fluorine-containing polymer, investigations have been made also with respect to adhesion of a fluorine-containing polymer to other inorganic material or adhesion or lamination to organic material.
However the fluorine-containing polymer inherently has low adhesive force, and it is difficult to adhere the fluorine-containing polymer directly to other material (substrate). Even if the adhering is tried by thermo-processing, adhesive strength of the fluorine-containing polymer is not enough, or even if the polymer has adhesive force to a certain extent, such an adhesive force is apt to vary depending on kind of the substrate. Thus in many cases, reliability on the adhesive strength of the fluorine-containing polymer has been not so enough.
In order to adhere the fluorine-containing polymer to other material, mainly the following methods have been studied:
1. a method for physically roughening a surface of substrate by sand blasting, etc.,
2. a method for surface-treating a fluorine-containing polymer by sodium etching, plasma treatment, photochemical treatment, etc.,
3. a method for adhering by using an adhesive, and other methods.
With respect to the methods 1 and 2 above, surface-treating steps are required, and the steps are complicated and productivity is poor. Also kinds and shapes of substrates are restricted. Further the obtained adhesive force is insufficient, and there easily occur problems with appearance of the obtained laminated article (coloring and flaw).
Use of an adhesive in the method 3 above has also been discussed. A usual hydrocarbon type adhesive does not have enough adhesive property and its heat resistance is insufficient. Thus a hydrocarbon type adhesive cannot stand under conditions for adhering of a fluorine-containing polymer which requires molding and processing at high temperature, and peeling due to decomposition of the adhesive and coloring occur. Since the laminated article made by using the adhesive also is insufficient in heat resistance, chemical resistance and water resistance of its adhesive layer, it cannot maintain adhesive force due to a change in temperature and environment, and lacks in reliability.
On the contrary, adhesion by using an adhesive composition comprising a fluorine-containing polymer having functional group is discussed.
For example, it is reported that a fluorine-containing polymer prepared by graft-polymerizing, to the fluorine-containing polymer, a hydrocarbon monomer which has carboxyl represented by maleic anhydride and vinyltrimethoxysilane, a residual group of carbonic acid, epoxy or a hydrolyzable silyl group, is used as an adhesive (for example, JP-A-7-18035, JP-A-7-25952, JP-A-7-25954, JP-A-7-173230, JP-A-7-173446, JP-A-7-173447) and that an adhesive composition comprising a fluorine-containing copolymer prepared by copolymerizing a hydrocarbon monomer having functional group such as hydroxyalkyl vinyl ether with tetrafluoroethylene or chlorotrifluoroethylene and an isocyanate hardening agent is cured and used as an adhesive between vinyl chloride resin and corona-discharged ETFE (for example, JP-A-7-228848).
The above-mentioned adhesive composition comprising a fluorine-containing polymer prepared by graft-polymerizing or copolymerizing a hydrocarbon monomer having functional group does not have enough heat resistance, and thus at the time of processing a laminated article comprising the adhesive composition and a fluorine-containing resin at high temperature or during use at high temperature, decomposition and foaming occur, thereby causing reduction of adhesive strength, peeling and coloring. In case of the adhesive composition disclosed in JP-A-7-228848, it is necessary to corona-discharge the fluorine-containing resin.
Also it is reported that a fluorine-containing polymer having functional group which is prepared by copolymerizing a perfluoro(vinyl ether) compound containing carboxylic acid or its derivative with a fluorine-containing monomer is used for an adhesive composition. U.S. Pat. No. 4,916,020 describes a laminated article produced by using a fluorine-containing polymer having functional group which is introduced by copolymerizing perfluoro(vinyl ether) having a carboxylic acid group or its derivative with tetrafluoroethylene.
That laminated article is one made by laminating the above-mentioned fluorine-containing polymer having a carboxylic acid group or the like to a metal or other substrate through a layer of an adhesive resin such as epoxy resin or urethane resin but not directly to a metal, glass or other resin. Therefore there is a problem with heat resistance, chemical resistance and solvent resistance of epoxy resin and urethane resin during use. If the lamination is carried out through epoxy resin or urethane resin, adhering is possible, but no method of directly adhering to a metal, glass or other resin is disclosed.
An object of the present invention is to solve the above-mentioned problems and provide a fluorine-containing adhesive which can give strong adhesion directly to metal, glass and resin substrates while maintaining excellent characteristics of a fluorine-containing polymer such as chemical resistance, solvent resistance, weather resistance and stain-proofing property and also to provide an adhesive film and a laminated article which are made by using the fluorine-containing adhesive. Further an object of the present invention is particularly to provide the fluorine-containing adhesive which can adhere to the above-mentioned substrates strongly through a step of adhering by thermo-melting and to provide the laminated article produced by using the fluorine-containing adhesive.
The present invention relates to a fluorine-containing adhesive comprising (A) a fluorine-containing ethylenic polymer having functional group which has a crystalline melting point or glass transition temperature of not more than 270xc2x0 C. and is prepared by copolymerizing:
(a) 0.05 to 30% by mole of at least one of fluorine-containing ethylenic monomers having at least one functional group selected from the group consisting of carboxyl and a carboxylic salt group and
(b) 70 to 99.95% by mole of at least one of fluorine-containing ethylenic monomers having no functional group mentioned above and copolymerizable with the component (a).
It is preferable that the fluorine-containing ethylenic monomer (a) having functional group is at least one of monomers which are represented by the formula (1):
CX2xe2x95x90CX1xe2x80x94Rfxe2x80x94COOYxe2x80x83xe2x80x83(1) 
wherein X and X1 are the same or different and each is hydrogen atom or fluorine atom, Y is hydrogen atom, NH4 or metal atom selected from elements of I, II, III, IVa and VIII groups, Rf is a divalent fluorine-containing alkylene group having 1 to 40 carbon atoms, a fluorine-containing oxyalkylene group having 1 to 40 carbon atoms, a fluorine-containing alkylene group having ether bond and 1 to 40 carbon atoms or a fluorine-containing oxyalkylene group having ether bond and 1 to 40 carbon atoms.
Further it is preferable that the fluorine-containing ethylenic monomer (b) which does not have the above-mentioned functional group is a monomer mixture of 40 to 80% by mole of tetrafluoroethylene or chlorotrifluoroethylene, 20 to 60% by mole of ethylene and 0 to 15% by mole of a monomer copolymerizable with those monomers.
Further it is preferable that the fluorine-containing ethylenic monomer (b) which does not have the above-mentioned functional group is vinylidene fluoride.
Further it is preferable that the fluorine-containing ethylenic monomer (b) which does not have the above-mentioned functional group is a monomer mixture comprising 70 to 99% by mole of vinylidene fluoride and 1 to 30% by mole of tetrafluoroethylene, a monomer mixture comprising 50 to 99% by mole of vinylidene fluoride, 0 to 30% by mole of tetrafluoroethylene and 1 to 20% by mole of chlorotrifluoroethylene or a monomer mixture comprising 60 to 99% by mole of vinylidene fluoride, 0 to 30% by mole of tetrafluoroethylene and 1 to 10% by mole of hexafluoropropylene.
The present invention also relates to the molded article made by melt-molding the above-mentioned fluorine-containing adhesive.
The present invention also relates to the fluorine-containing adhesive film made by melt-molding the above-mentioned fluorine-containing adhesive.
The present invention also relates to the laminated article comprising:
(A-2) a layer of the above-mentioned fluorine-containing adhesive and
(C-1) a layer of an inorganic material.
The present invention also relates to the laminated article comprising:
(A-3) a layer of the above-mentioned fluorine-containing adhesive and
(D-1) a layer of an organic material.
It is preferable that the inorganic material (C-1) is a metallic material.
It is preferable that the inorganic material (C-1) is a non-metallic inorganic material.
It is preferable that the inorganic material (C-1) is a glass material.
It is preferable that the organic material (D-1) is a non-fluorine-containing polymer.
It is preferable that the organic material (D-1) is a thermoplastic resin.
It is preferable that the organic material (D-1) is polyamide.
The present invention also relates to a laminated tube made by molding the above-mentioned laminated article into the form of tube.